Piston Type Compressor

ABSTRACT

Each suction port  43  of a cylinder block  11  has a narrow passage  50  located at a top dead center side and a wide passage  51  located at a bottom dead center side. A suction communication passage  45  of a rotary valve  41  passes by a first succeeding end  50   b  of the narrow passage  50  before passing by a second succeeding end  51   b  of the wide passage  51 . A high-pressure groove  47  of a residual gas bypass groove  46  faces only a narrow passage  50  of a suction port  43 A that corresponds to a high-pressure side compression chamber  26  when in communication with the suction port  43 A. A width Tc between the first succeeding end  50   b  and a second preceding end  51   a  of the wide passage  51  in the rotation direction of the rotary valve  41  is smaller than a seal width W of a seal region S between the high-pressure groove  47  and the outlet  45   b  of the suction communication passage  45 . This reduces the suction loss amount of gas in each compression chamber and improves the compression efficiency while advancing the timing at which the suction of gas into the compression chamber starts.

TECHNICAL FIELD

The present invention relates to a piston type compressor using a rotary valve, and more particularly, to a piston type compressor having a structure for bypassing gas remaining in a high-pressure side compression chamber after discharging is completed into a low-pressure side compression chamber.

BACKGROUND ART

Patent document 1 discloses a piston type compressor in which a rotation shaft rotates to reciprocate a piston in each cylinder bore. As a result, gas is drawn from a suction pressure region into compression chambers through a rotary valve, compressed in the compression chambers, and then discharged from the compression chambers. During a suction stroke, a suction communication passage of the rotary valve, which rotates in synchronization with the rotation shaft, sequentially communicates the suction pressure region with a passage extending from each compression chamber. The suction communication passage is elongated and extends in the axial direction of the rotary valve and has a uniform width.

An outer circumferential surface of the rotary valve includes a residual gas bypass groove that communicates a guide passage for a high-pressure side compression chamber after discharging is completed to a guide passage for a low-pressure side compression chamber. Non-discharged gas remaining in the compression chamber after discharging is completed, that is, residual gas, is bypassed or recovered in the low-pressure side compression chamber through the high-pressure side guide passage, the residual gas bypass groove, and the low-pressure side guide passage. This reduces re-expansion of gas in the compression chambers that occurs during the suction stroke. This ensures that gas is drawn from the suction pressure region into the compression chambers and improves the volumetric efficiency of the piston type compressor.

In the above piston type compressor, the passage of gas from a high-pressure opening of the residual gas bypass groove to the suction communication passage of the rotary valve via the guide passages in a cylinder block must be prevented. For this purpose, a seal region is formed in the outer circumferential surface of the rotary valve facing the guide passages of the cylinder block. The seal region closes the guide passages of the cylinder block between the high-pressure opening of the residual gas bypass groove and the suction communication passage of the rotary valve.

FIGS. 11 and 12 are development views showing a rotary valve 100 of which outer circumferential surface 100 a is laid out on a plane. A guide passage 101 of a cylinder block is in correspondence with the outer circumferential surface 100 a of the rotary valve 100. As shown in FIG. 11, the outer circumferential surface 100 a of the rotary valve 100 has a seal region S. The seal region S is required to have an area that is large enough to close an opening 101 a of the guide passage 101 in the cylinder block between a high-pressure opening 103 a of a residual gas bypass groove 103 and an opening 102 a of a suction communication passage 102 of the rotary valve.

As the area of the seal region S increases, a seal width W between the high-pressure opening 103 a and the suction communication passage 102 increases in the rotation direction of the rotary valve 100. In other words, the high-pressure opening 103 a becomes more distant from the opening 102 a of the suction communication passage 102. This increases the time difference between when the opening 101 a of the guide passage 101 in the cylinder block comes into communication with the high-pressure opening 103 a and the when the opening 101 a of the guide passage 101 comes into communication with the opening 102 a of the suction communication passage 102 in the rotary valve. The increase in the time difference indicates an increase in the time between when the gas in a high-pressure side compression chamber is recovered and when gas is drawn into the high-pressures side compression chamber. As a result, the timing at which gas is drawn into the compression chamber is delayed. This decreases the amount of gas drawn into the compression chambers and lower the compression efficiency.

Therefore, the area of the seal region S may be reduced, or more specifically, the seal width W may be reduced as shown in FIG. 12. This would reduce the time difference between the timing at which the opening 101 a of the guide passage 101 in the cylinder block starts communicating with the high-pressure opening 103 a and the timing at which the opening 101 a of the guide passage 101 starts communicating with the opening 102 a of the suction communication passage 102 in the rotary valve.

However, the seal region S is required to close the opening 101 a of the guide passage 101 in the cylinder block. Thus, if the area of the seal region S is just reduced, this would reduce the size of the opening 101 a in the guide passage 101. This is not desirable because the smaller opening 101 a would increase the suction loss of the gas drawn into the compression chambers and lower the compression efficiency.

Patent Document Japanese Laid-Open Patent Publication No. 2004-239210 DISCLOSURE OF THE INVENTION

It is an object of the present invention to provide a piston type compressor that reduces the suction loss of gas drawn into a compression chamber and improves the compression efficiency while advancing the timing for starting the suction of gas into the compression chamber.

One aspect of the present invention is a piston type compressor including a rotation shaft, a cylinder block having a plurality of cylinder bores arranged around the rotation shaft, a piston accommodated in each of the cylinder bores, and a rotary valve rotated in synchronization with the rotation shaft. The piston defines a compression chamber in the cylinder bore. The cylinder block has a plurality of suction ports, each of which communicates a suction pressure region to the corresponding compression chamber. The piston reciprocates between a bottom dead center that maximizes the volume of the compression chamber and a top dead center that minimizes the volume of the compression chamber so as to draw gas from the suction pressure region into the compression chamber through the rotary valve, compress the gas in the compression chamber, and discharge the gas from the compression chamber. The rotary valve has a suction communication passage and a residual gas bypass passage. The rotary valve is rotated so that the suction communication passage sequentially communicates each of the suction port with the suction pressure region and so that the residual gas bypass passage communicates the suction port corresponding to the compression chamber at the high-pressure side after discharging has been performed with the suction port corresponding to the compression chamber at the low-pressure side. A portion of an outer circumferential surface of the rotary valve facing openings of the suction ports forms a seal region that prevents the residual gas bypass passage from being communicated with the suction communication passage through the openings of the suction ports.

Each of the suction ports has a narrow passage located at a top dead center side and a wide passage located at a bottom dead center side. The narrow passage has an opening facing the outer circumferential surface of the rotary valve with a width in a rotation direction of the rotary valve that is smaller than a width of an opening of the wide passage. The opening of the narrow passage has a first preceding end and a first succeeding end. The suction communication passage of the rotating rotary valve first passes by the first preceding end and then passes by the first succeeding end. The opening of the wide passage has a second preceding end and a second succeeding end. The suction communication passage of the rotating rotary valve first passes by the second preceding end and then passes by the second succeeding end. The suction communication passage passes by the first succeeding end before passing by the second succeeding end. The residual gas bypass passage has a high-pressure opening. The high-pressure opening faces only the narrow passage of the suction port that corresponds to the high-pressure side compression chamber when in communication with the suction port. The narrow passage is arranged to enable communication with the compression chamber defined by the piston located at the top dead center. A width between the first succeeding end and the second preceding end in the rotation direction of the rotary valve is smaller than a dimension of a portion of the seal region between the high-pressure opening and an opening of the suction communication passage. The opening of the suction communication passage comes into communication with the wide passage immediately after the narrow passage is closed by the seal region.

Each of the suction ports may have a wide passage located at the top dead center side and a narrow passage located at the bottom dead center side. The wide passage may be arranged continuously with the narrow passage.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a vertical cross-sectional view showing a piston type compressor according to a first embodiment of the present invention;

FIG. 2 is a cross-sectional view taken along line 1-1 in FIG. 1;

FIG. 3 is a diagram showing a rotary valve of FIG. 1 of which outer circumferential surface is laid out on a plane;

FIG. 4 is a development view showing a state in which a narrow passage shown in FIG. 3 is closed by a seal region;

FIG. 5 is a development view showing a state in which a suction port is in communication with a suction communication passage;

FIG. 6 is a diagram showing a rotary valve according to a second embodiment of the present invention of which outer circumferential surface is laid out on a plane;

FIG. 7 is a diagram showing a rotary valve according to a third embodiment of the present invention of which outer circumferential surface is laid out on a plane;

FIG. 8 is a development view showing another example of a suction port;

FIG. 9 is a development view showing another example of a suction port;

FIG. 10 is a development view showing another example of a suction port;

FIG. 11 is a development view of a prior art rotary valve; and

FIG. 12 is a development view of a prior art rotary valve having a small region.

BEST MODE FOR CARRYING OUT THE INVENTION

A first embodiment of the present invention will now be described with reference to FIGS. 1 to 5. In the description hereafter, the directions of “up,” “down,” “front,” and “rear” for a piston type compressor 10 are indicated in FIG. 1 with the directions of arrows Y1 showing the upward and downward directions and the directions of arrows Y2 showing the frontward and rearward directions.

As shown in FIG. 1, the piston type compressor 10 includes a cylinder block 11, a front housing 12 joined to the front end of the cylinder block 11, and a rear housing 13 joined to the rear end of the cylinder block 11. A valve assembly 14 is arranged between the cylinder block 11 and the rear housing 13. The cylinder block 11, the front housing 12, the rear housing 13, and the valve assembly 14 are fastened together by a plurality of bolts B. FIG. 1 shows only one of the bolts B. The cylinder block 11, the front housing 12, and the rear housing 13 form a housing for the piston type compressor 10.

In the housing, a space defined in the front housing 12 and the cylinder block 11 defines a crank chamber 17. A rotation shaft 19 is rotatably supported by the cylinder block 11 and the front housing 12. The rotation shaft 19 is arranged in the crank chamber 17. The rotation shaft 19 is operably connected to an external drive source, for example, an engine E, by a power transmission mechanism PT. The rotation shaft 19 rotates when supplied with power from the external drive source E. The rotation shaft 19 is inserted through a shaft hole 20 extending through the cylinder block 11 and a shaft hole 21 extending through the front housing 12.

The rotation shaft 19 has a front end supported by the front housing 12 with a radial bearing 22, which is arranged in the shaft hole 20 of the front housing 12. A lip-seal type shaft seal unit 23 is arranged between the front housing 12 and the rotation shaft 19. The shaft seal unit 23 prevents leakage of refrigerant gas from the crank chamber 17 along the rotation shaft 19. A lug plate 16 is fixed on the rotation shaft 19 in the crank chamber 17 in a manner that the lug plate 16 rotates integrally with the rotation shaft 19. A thrust bearing 18 is arranged between the lug plate 16 and the front housing 12.

A swash plate 24 is accommodated in the crank chamber 17. The swash plate 24 is supported on the rotation shaft 19 in a manner that the swash plate 24 is slidable and tiltable on the rotation shaft 19 such that its inclination angle relative to a central axis L1 of the rotation shaft 19 is variable. A hinge mechanism 25 is arranged between the lug plate 16 and the swash plate 24. The swash plate 24, which is hinge-connected to the lug plate 16 by the hinge mechanism 25, is supported by the rotation shaft 19 and is rotatable in synchronization with the lug plate 16 and the rotation shaft 19. Further, the swash plate 24 is tiltable with respect to the rotation shaft 19 while sliding in the axial direction of the rotation shaft 19, or in the direction of the central axis L1.

As shown in FIG. 2, the cylinder block 11 includes a plurality of, five in the present embodiment, cylinder bores 11 a arranged around the rotation shaft 19. Each cylinder bore 11 a accommodates a single-headed piston 31 in a manner enabling reciprocation. Each piston 31 is coupled to the peripheral portion of the swash plate 24 in a tiltable manner by a pair of front and rear shoes 30. The rotation of the swash plate 24, which occurs when the rotation shaft 19 rotates, is converted to the reciprocation of each piston 31 by the shoes 30.

The front and rear openings of each cylinder bore 11 a are closed by the valve assembly 14 and the corresponding piston 31. A compression chamber 26 defined in the cylinder bore 11 a changes its volume as the piston 31 reciprocates. A suction passage 28, which serves as a suction pressure region, and a discharge chamber 29 are defined in the rear housing 13. The suction passage 28 is formed in the central portion of the rear housing 13. The discharge chamber 29 is formed to surround the outer circumference of the suction passage 28. The valve assembly 14 includes discharge ports 32 and discharge valves 33. The discharge ports 32 communicate the compression chambers 26 with the discharge chamber 29. The discharge valves 33 open and close the discharge ports 32.

A rotary valve 41 and a residual gas bypass passage will now be described.

A valve accommodation chamber 42 surrounded by the cylinder bores 11 a is defined in the central portion of the cylinder block 11. The rotary valve 41 is accommodated in a rotatable manner within the valve accommodation chamber 42. A plurality of suction ports 43 extending through the cylinder block 11 communicate the valve accommodation chamber 42 with each compression chamber 26. FIG. 1 shows only one of the suction ports 43. The rotary valve 41, which is made of a metal material containing aluminum, is cylindrical. The rotation shaft 19 has a rear end arranged in the valve accommodation chamber 42. The rotary valve 41 has a front end pressed fitted into a press-fitting recess 19 a formed in the rear end of the rotation shaft 19.

An outer circumferential surface 41 a of the rotary valve 41 and a circumferential surface 42 a of the valve accommodation chamber 42 form a slide bearing surface for supporting the rotary valve 41 in a rotatable manner within the valve accommodation chamber 42. The rear end of the rotation shaft 19 is supported on the cylinder block 11 by the rotary valve 41 in a rotatable manner. The rotary valve 41 has a central axis L2 that is coaxial with the central axis L1 of the rotation shaft 19. In other words, the rotary valve 41 and the rotation shaft 19 are integrated to form a coaxial structure. The rotary valve 41 rotates in synchronization with the rotation of the rotation shaft 19, that is, in synchronization with the reciprocation of the pistons 31.

The rotary valve 41 includes an inner space 44. The inner space 44 is in communication with the suction passage 28 through a hole 14 a formed in the valve assembly 14. As shown in FIG. 2, a suction communication passage 45, which extends from the inner space 44 to the outer circumferential surface 41 a of the rotary valve 41, is formed in the peripheral wall of the rotary valve 41. More specifically, an inlet 45 a of the suction communication passage 45 opens into the inner space 44, and an outlet 45 b of the suction communication passage 45 opens to the outer circumferential surface 41 a of the rotary valve 41. As the rotation of the rotary valve 41 rotates the rotation shaft 19, the outlet 45 b of the suction communication passage 45 is intermittently communicated with the openings, or inlets 43 a, of the suction ports 43 of the cylinder block 11. More specifically, the suction communication passage 45 sequentially communicates the inner space 44, which functions as a suction pressure region, with the inlets 43 a of the suction ports 43 extending from the compression chambers 26 in synchronization with the rotation of the rotary valve 41.

The outlet 45 b of the suction communication passage 45 of the rotary valve 41 is in communication with the inlets 43 a of the suction ports 43 of the cylinder block 11 when a piston 31 shifts to the suction stroke. Then, refrigerant gas from the suction passage 28 flows sequentially through the hole 14 a of the valve assembly 14, the inner space 44 of the rotary valve 41, the suction communication passage 45, and the suction port 43 in the cylinder block 11 to be drawn into the compression chamber 26.

In the suction stroke, the position of a piston 31 at which the volume of its compression chamber 26 becomes maximum is referred to as the bottom dead center of the piston 31. When the suction stroke of the piston 31 is completed, that is, when the piston 31 is located at the bottom dead center, the outlet 45 b in the suction communication passage 45 of the rotary valve 41 is completely separated from the inlet 43 a of the suction port 43 of the cylinder block 11 in the circumferential direction. In this state, the suction of refrigerant gas from the inner space 44 into the compression chamber 26 is suspended. Afterwards, as the piston 31 shifts to the compression stroke and the discharge stroke, the outer circumferential surface 41 a of the rotary valve 41 keeps the inner space 44 closed from the compression chamber 26. Thus, there is not interference with the compression of the refrigerant gas and discharging of the compressed gas into the discharge chamber 29. In the compression stroke and the discharge stroke, the position of the piston 31 at which the volume of its compression chamber 26 becomes minimum is referred to as the top dead center of the piston 31. When the piston 31 is located at the top dead center, the so-called top clearance exists between the valve assembly 14 and the piston 31 in the cylinder bore 11 a. Residual gas that was not discharged remains in the top clearance of the compression chamber 26.

FIG. 3 is a diagram showing the rotary valve 41 of which the outer circumferential surface 41 a is laid out on a plane. The suction port 43 of the cylinder block 11 faces the outer circumferential surface 41 a of the rotary valve 41. In FIGS. 3 to 5, the direction of arrow Y3 in FIG. 3 indicates the rotation direction of the rotary valve 41, or the circumferential direction. The rotary valve 41 moves to the left as viewed in FIG. 3. The directions of arrow Y4 indicate the axial direction of the rotary valve 41, that is, the direction of the central axis L2.

As shown in FIG. 3, a residual gas bypass groove 46, which functions as a residual gas bypass passage, is formed in the outer circumferential surface 41 a of the rotary valve 41. The residual gas bypass groove 46 includes a high-pressure groove 47, a low-pressure groove 48, and a communication groove 49. The high-pressure groove 47 extends in the direction of central axis L2 of the rotary valve 41, that is, in the direction of arrow Y4, and functions as a high-pressure opening. The low-pressure groove 48 also extends in the direction of the central axis L2. The communication groove 49 extends in the circumferential direction of the rotary valve 41, that is, the direction of the arrow Y3, and communicates an end of the high-pressure groove 47 at the top dead center side with an end of the low-pressure groove 48 at the top dead center side. In other words, the communication groove 49 communicates the end of the high-pressure groove 47 at the rear side of the piston type compressor 10 with the end of the low-pressure groove 48 at the rear side of the piston type compressor 10.

The high-pressure groove 47 is arranged in the outer circumferential surface 41 a of the rotary valve 41 so as to come into communication with the suction port 43 (43A) that corresponds to the high-pressure side compression chamber 26 immediately after discharging is performed, before the low-pressure groove 48 communicates with the suction port 43. Thus, the high-pressure groove 47 comes into communicates with the top clearance of the cylinder bore 11 a through the suction port 43 of the cylinder block 11. Further, the low-pressure groove 48 is arranged in the outer circumferential surface 41 a of the rotary valve 41 to face the suction port 43 (43B) that corresponds to the compression chamber 26 that has just completed suction, that is, the low-pressure side compression chamber 26.

The outer circumferential surface 41 a of the rotary valve 41 includes a seal region S located between the high-pressure groove 47 and the suction communication passage 45 of the rotary valve 41. The seal region S prevents the passage of gas from the high-pressure groove 47 of the residual gas bypass groove 46 to the outlet 45 b of the suction communication passage 45 of the rotary valve 41 through the inlet 43 a of a suction port 43 in the cylinder block 11. The seal region S on the outer circumferential surface 41 a of the rotary valve 41 faces the inlets 43 a of the suction ports 43, and separates the high-pressure groove 47 from the outlet 45 b of the suction communication passage 45. The non-discharged refrigerant gas remaining in a compression chamber 26 immediately after discharging is performed flows sequentially through a suction port 43 (43A) in the cylinder block 11, the high-pressure groove 47 of the rotary valve 41, the communication groove 49, the low-pressure groove 48, and a suction port 43 (43B) of the cylinder block 11 and is then bypassed to or recovered in the compression chamber 26 that has just completed suction.

As indicated by the double-dashed lines in FIG. 3, each suction port 43, which extends through the cylinder block 11, has an opening, or an inlet 43 a, facing the outer circumferential surface 41 a of the rotary valve 41. The inlet 43 a has two different opening widths Ta and Tb. The suction port 43 includes a narrow passage 50 and a wide passage 51. The narrow passage 50 is arranged at the top dead center side and the wide passage 51 at the bottom dead center side in the direction of the central axis L2 of the rotary valve 41. More specifically, the suction port 43 has a top dead center side passage at the top dead center side and a bottom dead center side passage at the bottom dead center side. In the first embodiment, the top dead center side passage is the narrow passage 50, and the bottom dead center passage is the wide passage 51.

The narrow passage 50, which has the first opening width Ta that is uniform in the circumferential direction of the rotary valve 41, extends in the direction of the central axis L2. The wide passage 51, which has the second opening width Tb that is uniform in the circumferential direction, extends in the direction of the central axis L2. At the inlet 43 a of the suction port 43, the first opening width Ta of the narrow passage 50 is set to be narrower than the second opening width Tb of the wide passage 51 (Ta<Tb).

The first opening width Ta of the narrow passage 50 is set to be smaller than the distance between the high-pressure groove 47 and the suction communication passage 45 in the circumferential direction, that is, a seal width W of a portion of the seal region S (W>Ta). The second opening width Tb of the wide passage 51 is set to greater than the seal width W (W<Tb). The boundary between the narrow passage 50 and the wide passage 51 at the inlet 43 a of the suction port 43 is formed in a stepped manner. When the rotary valve 41 rotates, the high-pressure groove 47 passes by the portion located toward the top dead center side, or the lower side as viewed in FIG. 3, from the wide passage 51. Thus, the high-pressure groove 47 is formed to come into communication with the narrow passage 50 but not with the wide passage 51 when the rotary valve 41 rotates.

The narrow passage 50 has a first preceding end 50 a and a first succeeding end 50 b opposite the first preceding end 50 a in the rotation direction of the rotary valve 41. When the rotary valve 41 rotates, the suction communication passage 45 first passes by the first preceding end 50 a and then passes by the first succeeding end 50 b. In the same manner, the wide passage 51 has a second preceding end 51 a and a second succeeding end 51 b opposite the second preceding end 51 a in the rotation direction of the rotary valve 41. When the rotary valve 41 rotates, the suction communication passage 45 first passes by the second preceding end 51 a and then passes by the second succeeding end 51 b. The first preceding end 50 a side with respect to the first succeeding end 50 b is referred to as the preceding side, and the side opposite the preceding side is referred to as the succeeding side. The second preceding end 51 a side with respect to the second succeeding end 51 b is referred to as the preceding side, and the side opposite the preceding side is referred to as the succeeding side.

A third opening width Tc from the first succeeding end 50 b of the narrow passage 50 to the second preceding end 51 a of the wide passage 51 in the rotation direction of the rotary valve 41 is set to be slightly smaller than the seal width W of the seal region S. Thus, the outlet 45 b of the suction communication passage 45 comes into communication with the wide passage 51 immediately after the high-pressure groove 47 passes by the narrow passage 50.

FIG. 3 shows a state in which the compression chamber 26 corresponding to the suction port 43A has just undergone discharging, and the piston 31 in this high-pressure side compression chamber 26 is located at the top dead center. At this timing, the high-pressure groove 47 passes by the top dead center side from the wide passage 51. More specifically, the high-pressure groove 47 comes into communication with only the narrow passage 50 and does not come into communication with the wide passage 51 at the inlet 43 a of the suction port 43. The wide passage 51 at the inlet 43 a of the suction port 43 is closed by the seal region S. The non-discharged residual refrigerant gas remaining in the top clearance of the compression chamber 26 sequentially flows through the suction port 43A of the cylinder block 11, the high-pressure groove 47 of the rotary valve 41, the communication groove 49, the low-pressure groove 48, and the suction port 43B of the cylinder block 11 and is then bypassed or recovered in the compression chamber 26 immediately after suction has been completed. This reduces re-expansion of the residual gas during the suction stroke of the compression chamber 26 that corresponds to the suction port 43A. This ensures that refrigerant gas is drawn from the compression chamber 26 into the inner space 44 and improves the volumetric efficiency of the piston type compressor 10.

Afterwards, as shown in FIG. 4, the rotary valve 41 rotates and the high-pressure groove 47 passes by the narrow passage 50 so that the narrow passage 50 at the inlet 43 a of the suction port 43 is closed by the seal region S. In this state, the wide passage 51 at the inlet 43 a of the suction port 43 has already been closed by the seal region S. Thus, the narrow passage 50 and the wide passage 51, that is, the entire inlet 43 a of the suction port 43, is closed by the seal region S. The seal region S prevents gas passage between the high-pressure groove 47 and the outlet 45 b of the suction communication passage 45 through the inlet 43 a of the suction port 43.

When the rotary valve 41 rotates slightly from the state shown in FIG. 4, the outlet 45 b of the suction communication passage 45 comes into communication with the wide passage 51. More specifically, immediately after the high-pressure groove 47 passes by the narrow passage 50, or immediately after the high-pressure groove 47 is separated from the inlet 43 a of the suction port 43A, the outlet 45 b of the suction communication passage 45 comes into communication with the inlet 43 a of the suction port 43A. FIG. 5 shows the state in which both the narrow passage 50 and the wide passage 51 come into communication with the suction communication passage 45 of the rotary valve 41 after further rotation of the rotary valve 41. Then, when the rotary valve 41 rotates further, the entire inlet 43 a of the suction port 43A, that is, the entire narrow passage 50 and the entire wide passage 51, comes into communication with the outlet 45 b of the suction communication passage 45. Refrigerant gas sequentially flows from the suction passage 28 to the hole 14 a of the valve assembly 14, the inner space 44 of the rotary valve 41, the suction communication passage 45, and the suction port 43A of the cylinder block 11 to be drawn into the compression chamber 26.

The first embodiment has the advantages described below.

(1) The inlet 43 a of the suction port 43 includes the top dead center side narrow passage 50 and the bottom dead center side wide passage 51. More specifically, the top dead center side width Ta of the inlet 43 a of the suction port 43 in the rotation direction of the rotary valve 41, that is, the circumferential direction, is set to be smaller than the bottom dead side width Tb of the inlet 43 a. The high-pressure groove 47 is formed to communicate with only the narrow passage 50 when the rotary valve 41 rotates. The width Ta of the opening of the narrow passage 50 is smaller than the width Tb of the opening of the wide passage 51. This reduces the seal width W of the seal region S for preventing gas passage. As a result, the distance between the high-pressure groove 47 and the outlet 45 b of the suction communication passage 45 of the rotary valve 41 may be shortened. This reduces the time difference between the timing at which the high-pressure groove 47 of the rotary valve 41 comes into communication with the suction port 43A of the cylinder block 11 at the narrow passage 50 and the timing at which the suction communication passage 45 of the rotary valve 41 comes into communication with the suction port 43A of the cylinder block 11 at the wide passage 51. More specifically, this reduces the time difference from when the residual gas in the high-pressure side compression chamber 26 corresponding to the suction port 43A is recovered to when the suction of refrigerant gas into the high-pressure side compression chamber 26 starts.

To prevent the passage of gas from the high-pressure groove 47 to the suction communication passage 45, the seal region S is only required to close the narrow passage 50. Thus, the suction port 43 may include the wide passage 51 in addition to the narrow passage 50. Even when the seal width W of the seal region S is set to be small in order to advance the timing at which the refrigerant gas starts to be drawn into the compression chambers 26, the suction loss of the refrigerant gas is prevented from increasing. This structure reduces the suction loss amount of gas and improves the compression efficiency while advancing the timing at which the refrigerant gas starts being drawn into the compression chamber 26.

(2) The narrow passage 50 is arranged continuously with the wide passage 51 at the inlet 43 a of the suction port 43. Thus, as compared with when, for example, the narrow passage 50 is separated from the wide passage 51, the suction amount of refrigerant gas from the inlet 43 a of the suction port 43 into the compression chamber 26 increases.

(3) As shown in FIG. 3, when the piston 31 is located at the top dead center, the narrow passage 50 at the inlet 43 a of the suction port 43 is in direct communication with the compression chamber 26. Thus, when the high-pressure groove 47 comes into communication with the narrow passage 50, the residual gas in the compression chamber 26 is readily recovered in the high-pressure groove 47. This ensures the recovery of the residual gas. Thus, re-expansion of the residual gas that occurs during the suction stroke is reduced, and refrigerant gas is drawn into each compression chamber 26 in an ensured manner. As a result, the volumetric efficiency of the piston type compressor 10 is improved.

A piston type compressor according to a second embodiment of the present invention will now be described with reference to FIG. 6. The piston type compressor of the second embodiment differs from the piston type compressor 10 of the first embodiment only in the structure of each suction port 43. Components that are the same as the first embodiment will not be described.

As shown in FIG. 6, at the inlet 43 a of the suction port 43 in the second embodiment, a narrow passage 50 is formed closer to the preceding side of a wide passage 51 in the rotation direction of the rotary valve 41. In other words, the narrow passage 50 is arranged closer to the second preceding end 51 a of the wide passage 51. In the second embodiment, a first preceding end 50 a of the narrow passage 50 lies along the same straight line as the second preceding end 51 a of the wide passage 51. The first opening width Ta of the narrow passage 50 and the second opening width Tb of the wide passage 51 are set the same to be the same as in the first embodiment.

The seal width W of a portion of a seal region S between a high-pressure groove 47 and a suction communication passage 45 is set to be slightly greater than the third opening width Tc. The third opening width Tc, which is the distance from the first succeeding end 50 b of the narrow passage 50 to the second preceding end 51 a of the wide passage 51, is equal to the distance from the first succeeding end 50 b to the first preceding end 50 a of the narrow passage 50 (Ta=Tc). In this manner, the seal width W of the seal region S in the second embodiment is set to be smaller than in the first embodiment.

The second embodiment further has the advantage described below.

(4) As shown in FIG. 6, the narrow passage 50 in the second embodiment is arranged closer to the first preceding end 50 a of the wide passage 51 as compared with the first embodiment. The seal width W in the second embodiment is set to be smaller than the seal width W in the first embodiment. Thus, the distance between the high-pressure groove 47 and the outlet 45 b of the suction communication passage 45 is further reduced. This further reduces the time difference between when the high-pressure groove 47 of the rotary valve 41 comes into communication with the narrow passage 50 of the cylinder block 11 and when the suction communication passage 45 of the rotary valve 41 comes into communication with the suction port 43 of the cylinder block 11. As a result, the suction loss amount of gas into each compression chamber 26 is reduced.

A piston type compressor according to a third embodiment of the present invention will now be described with reference to FIG. 7. The piston type compressor of the third embodiment differs from the piston type compressor of the first embodiment in that the positional relationship of the narrow passage 50 and the wide passage 51 is reversed in terms of the top dead center side and the bottom dead center side, and the positional relationship between the suction port 43 and the residual gas bypass groove 46 is reversed in terms of the top dead center side and the bottom dead center side. The components of the third embodiment that are the same as those in the first embodiment will not be described.

As shown in FIG. 7, the high-pressure groove 47 and low-pressure groove 48 of the residual gas bypass groove 46 in the outer circumferential surface 41 a of the rotary valve 41 are located at a bottom dead center side of the suction port 43 with respect to the direction of the center axis L2 of the rotary valve 41. More specifically, the high-pressure groove 47, which functions as a high-pressure opening, is arranged toward the front of the piston type compressor 10 from the suction port 43. A communication groove 49 of the residual gas bypass groove 46 communicates the ends of the high-pressure groove 47 and the low-pressure groove 48 at the bottom dead center side. More specifically, the communication groove 49 communicates the front ends of the high-pressure groove 47 and the low-pressure groove 48 in the piston type compressor 10.

As indicated by the double-dashed lines in FIG. 7, an inlet 43 a of each suction port 43 extending through the cylinder block 11 has two different opening widths Ta and Tb. More specifically, the opening of the suction port 43 facing the outer circumferential surface 41 a of the rotary valve 41 has two different opening widths Ta and Tb. The inlet 43 a of the suction port 43 has a narrow passage 50 arranged at the bottom dead center side and a wide passage 51 at the top dead center side in the direction of the central axis L2 of the rotary valve 41. The narrow passage 50, which extends in the direction of the central axis L2, has the first opening width Ta that is uniform in the circumferential direction of the rotary valve 41. The wide passage 51, which extends in the direction of the central axis L2, has the second opening width Tb that is uniform in the circumferential direction.

The first opening width Ta of the narrow passage 50 is set to be smaller than the seal width W of the seal region S (W>Ta). The second opening width Tb of the wide passage 51 is set to be greater than the seal width W of the seal region S (W<Tb). The narrow passage 50 is continuous with the wide passage 51 at the inlet 43 a of the suction port 43. The boundary between the narrow passage 50 and the wide passage 51 is formed in a stepped manner. When the rotary valve 41 rotates, the high-pressure groove 47 passes by the portion located toward the bottom dead center side, or the upper side as viewed in FIG. 7, from the wide passage 51. Thus, the high-pressure groove 47 comes into communication with the narrow passage 50 but not with the wide passage 51 when the rotary valve 41 rotates.

A third opening width Tc between the first succeeding end 50 b of the narrow passage 50 and the second preceding end 51 a of the wide passage 51 in the circumferential direction is set to be slightly smaller than the seal width W of the seal region S. Thus, the outlet 45 b of the suction communication passage 45 comes into communication with the wide passage 51 immediately after the high-pressure groove 47 passes by the narrow passage 50. The wide passage 51 arranged at the lower side as viewed in FIG. 7, or the bottom dead center side, comes into direct communication with the compression chamber 26 immediately after discharging is performed when the piston 31 is located at the top dead center.

The third embodiment further has the advantage described below.

(5) The wide passage 51 is formed toward the top dead center side from the narrow passage 50 in the direction of the central axis L2 of the rotary valve 41. Thus, as compared with the first embodiment, the first embodiment increases the area of the suction port 43 of the cylinder block 11 that communicates with the suction communication passage 45 of the rotary valve 41 when refrigerant gas starts to be drawn into the compression chamber 26. As a result, the amount of gas drawn into the compression chamber 26 increases. In the first embodiment, the narrow passage 50 is formed toward the top dead center side from the wide passage 51, and the first preceding end 50 a is formed at the succeeding side of the second preceding end 51 a of the wide passage 51.

The above embodiments may be modified as described below.

In the above embodiments, the narrow passage 50 may be formed by a plurality of small passages that are separated from one another as shown in FIG. 8. In this case, a first opening width Ta of the narrow passage 50 is the distance between a first preceding end 50 a of the most preceding one of the small passages and a first succeeding end 50 b of the most succeeding one of the small passages. The first preceding end 50 a and a second preceding end 51 a lie along the same line. Thus, Ta=Tc is satisfied. A third opening width Tc is required only to be set smaller than the seal width W between a high-pressure groove 47 and a suction communication passage 45.

As shown in FIG. 9, in the first and second embodiments, the narrow passage 50 may be formed by a pair of elongated holes. That is, the shape of the narrow passage 50 is not limited to the shape illustrated in the first to third embodiments and may be, for example, an oval hole or a circular hole.

As shown in FIG. 9, the narrow passage 50 may be separated from the wide passage 51. For example, the narrow passage 50 may be formed by two small passages that are elongated holes extending in the circumferential direction of the rotary valve 41. The first preceding end 50 a is defined by the most preceding end of the small passages, and the first succeeding end 50 b is defined by the most succeeding end of the small passages. A third opening width Tc of the narrow passage 50 is the distance between the second preceding end 51 a of the wide passage 51 and the first succeeding end 50 b of the narrow passage 50. The third opening width Tc is only required to be smaller than the seal width W between the high-pressure groove 47 and suction communication passage 45.

As shown in FIG. 10, the opening width of the wide passage 51, that is, the circumferential direction dimension, may decrease as the narrow passage 50 becomes closer. In FIG. 10, the second preceding end 51 a and second succeeding end 51 b of the wide passage 51 are formed by a portion of the wide passage 51 that has the maximum opening width, that is, the end of the wide passage 51 at the bottom dead center.

In the third embodiment, the narrow passage 50 may be formed closer to the preceding side of the wide passage 51, or the second preceding end 51 a, in the rotation direction of the rotary valve 41. The first preceding end 50 a of the narrow passage 50 may lie along the same straight line as the second preceding end 51 a of the wide passage 51.

In the above embodiments, the suction port 43 is only required to have the narrow passage 50 and the wide passage 51 at the inlet 43 a, and the shape of the outlet of the suction port 43 or the shape of the passage within the suction port 43 may be modified freely.

In the above embodiments, the first succeeding end 50 b of the narrow passage 50 is only required to be located toward the preceding side from the second succeeding end 51 b of the wide passage 51, and the narrow passage 50 may be formed closer to the succeeding side of the wide passage 51.

The present invention may be applied to a double-headed piston type compressor. 

1. A piston type compressor comprising a rotation shaft, a cylinder block having a plurality of cylinder bores arranged around the rotation shaft, a piston accommodated in each of the cylinder bores, and a rotary valve rotated in synchronization with the rotation shaft; wherein the piston defines a compression chamber in the cylinder bore, the cylinder block (has a plurality of suction ports each of which communicates a suction pressure region to the corresponding compression chamber, and the piston reciprocates between a bottom dead center that maximizes the volume of the compression chamber and a top dead center that minimizes the volume of the compression chamber so as to draw gas from the suction pressure region into the compression chamber through the rotary valve, compress the gas in the compression chamber, and discharge the gas from the compression chamber; and the rotary valve has a suction communication passage and a residual gas bypass passage, the rotary valve is rotated so that the suction communication passage sequentially communicates each of the suction port with the suction pressure region and so that the residual gas bypass passage communicates the suction port corresponding to the compression chamber at the high-pressure side after discharging has been performed with the suction port corresponding to the compression chamber at the low-pressure side, and a portion of an outer circumferential surface of the rotary valve facing openings of the suction ports forms a seal region that prevents the residual gas bypass passage from being communicated with the suction communication passage through the openings of the suction ports, the piston type compressor being characterized in that: each of the suction ports has a narrow passage located at a top dead center side and a wide passage located at a bottom dead center side, the narrow passage has an opening facing the outer circumferential surface of the rotary valve with a width in a rotation direction of the rotary valve that is smaller than a width of an opening of the wide passage; the opening of the narrow passage has a first preceding end and a first succeeding end, wherein the suction communication passage of the rotating rotary valve first passes by the first preceding end and then passes by the first succeeding end, and the opening of the wide passage has a second preceding end and a second succeeding end, wherein the suction communication passage of the rotating rotary valve first passes by the second preceding end and then passes by the second succeeding end; the suction communication passage passes by the first succeeding end before passing by the second succeeding end; the residual gas bypass passage has a high-pressure opening, and the high-pressure opening faces only the narrow passage of the suction port that corresponds to the high-pressure side compression chamber when in communication with the suction port; the narrow passage is arranged to enable communication with the compression chamber defined by the piston located at the top dead center; and a width between the first succeeding end and the second preceding end in the rotation direction of the rotary valve is smaller than a dimension of a portion of the seal region between the high-pressure opening and an opening of the suction communication passage, and the opening of the suction communication passage comes into communication with the wide passage immediately after the narrow passage is closed by the seal region.
 2. The piston type compressor according to claim 1, wherein the wide passage is arranged continuously with the narrow passage.
 3. The piston type compressor according to claim 1, wherein the narrow passage is arranged closer to the second preceding end with respect to the wide passage.
 4. The piston type compressor according to claim 3, wherein the first preceding end and the second preceding end lie along the same straight line.
 5. A piston type compressor comprising a rotation shaft, a cylinder block having a plurality of cylinder bores arranged around the rotation shaft, a piston accommodated in each of the cylinder bores, and a rotary valve rotated in synchronization with the rotation shaft; wherein the piston defines a compression chamber in the cylinder bore, the cylinder block has a plurality of suction ports each of which communicates a suction pressure region to the corresponding compression chamber, and the piston reciprocates between a bottom dead center that maximizes the volume of the compression chamber and a top dead center that minimizes the volume of the compression chamber so as to draw gas from the suction pressure region into the compression chamber through the rotary valve, compress the gas in the compression chamber, and discharge the gas from the compression chamber; and the rotary valve has a suction communication passage and a residual gas bypass passage, the rotary valve is rotated so that the suction communication passage sequentially communicates each of the suction port with the suction pressure region and so that the residual gas bypass passage communicates the suction port corresponding to the compression chamber at the high-pressure side after discharging has been performed with the suction port corresponding to the compression chamber at the low-pressure side, and a portion of an outer circumferential surface of the rotary valve facing openings of the suction ports forms a seal region that prevents the residual gas bypass passage from being communicated with the suction communication passage through the openings of the suction ports, the piston type compressor being characterized in that: each of the suction ports has a wide passage located at a top dead center side and a narrow passage located at a bottom dead center side, the narrow passage has an opening facing the outer circumferential surface of the rotary valve with a width in a rotation direction of the rotary valve that is smaller than a width of an opening of the wide passage; the opening of the narrow passage has a first preceding end and a first succeeding end, wherein the suction communication passage of the rotating rotary valve first passes by the first preceding end and then passes by the first succeeding end, and the opening of the wide passage has a second preceding end and a second succeeding end, wherein the suction communication passage of the rotating rotary valve first passes by the second preceding end and then passes by the second succeeding end; the suction communication passage passes by the first succeeding end before passing by the second succeeding end; the residual gas bypass passage has a high-pressure opening, and the high-pressure opening faces only the narrow passage of the suction port that corresponds to the high-pressure side compression chamber when in communication with the suction port; the wide passage is arranged continuously with the narrow passage, and the wide passage is arranged to enable communication with the compression chamber defined by the piston located at the top dead center; and a width between the first succeeding end and the second preceding end in the rotation direction of the rotary valve is smaller than a dimension of a portion of the seal region between the high-pressure opening and an opening of the suction communication passage, and the opening of the suction communication passage comes into communication with the wide passage immediately after the narrow passage is closed by the seal region.
 6. The piston type compressor according to claim 5, wherein the narrow passage is arranged closer to the second preceding end with respect to the wide passage.
 7. The piston type compressor according to claim 6, wherein the first preceding end and the second preceding end lie along the same straight line.
 8. The piston type compressor according to claim 2, wherein the narrow passage is arranged closer to the second preceding end with respect to the wide passage.
 9. The piston type compressor according to claim 8, wherein the first preceding end and the second preceding end lie along the same straight line. 